7715

• UCREFRP Catalog Number: 7715
• Author: U.S. Fish and Wildlife Service, C. R. F. R. T.
• Title: Bonytail Chub Recovery Plan.
• USFW Year: 1990.
• USFW - Doc Type: \
• Copyright Material: NO

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and Colorado Division of Wildlife (Wick et al. 1979, 1981). However, in 1984
a single bony tail chub was collected from the Black Rocks area of the Colorado
River (Kaeding et al. 1986). Several suspected bony tail chub also have been
captured in Cataract Canyon of the Colorado River within 32 kilometers
(20 miles) upstream of the inflow to Lake Powell. This includes two in 1985
(one adult 386 mm [15 in.] TL and one juvenile 46 mm [2 in.] TL) (Valdez
1985), one in 1986 (383 mm [15 in.] TL) (Valdez 1987), and two in 1987 (one
adult 287 mm [11 in.] TL, one juvenile 264 mm [10 in.] Tl) (Valdez 1988).
Ongoing studies in this canyon area may reveal additional specimens.

Studies of the lower San Juan River (VTN 1978; Bureau of Reclamation 1987
[unpublished]) did not reveal any bony tail chub. However, a bony tail chub was
caught by an angler near Wawheap Marina, Lake Powell, in May 1985 (Randy
Radant, Utah Division of Wildlife, pers. comm.).

life History

This discussion is separated into three sections (riverine, reservoir, and
hatchery) so that differences in observed life history requirements can be
correlated with habitat.

Riverine

Bony tail chub always have been considered big- or mainstem river sDecies.
Vanicek (1967) noted that adult bony tail chub occupied Dools and eddies rather
than areas with more current. Spawning of bony tail chub has not been observed
in a river, but extrapolation from a collection of ripe fish suggested that
spawninq occurred in Dinosaur National Monument during late June and earl~
~ulY at water temperatures of about ~(640F) (Vanice~and Kramer 1969).

Vanicek and Kramer (1969) estimated growth rates of bony tail chub by
back-calculation of total length based on proportional growth of sc les.
Young were 55 mm (2 in.) their first growing season, 100 mm (4 in.) their
second season, and 158 mm (6 in.) their third season in the Green River at
Dinosaur National Monument. The largest bony tail chub handled by Vanicek and
Kramer (1969) was 388 mm (15 in.) and 7 years old. Scale readings are valid
for the first several years of life, but annuli cannot be separated accurately
in older fish. Three specimens from Lake Mohave were estimated to be between
34 to 49 years old based on otolith examination (Minckley 1985).

In the Green River at Dinosaur National Monument, Vanicek and Kramer (1969)
found that ~ounq chubs, including bony tail and roundtail chubs, ate primarily
chironomid larvae. and mayfly nymphs. Small fish became more dependent on
floating food items as they grew larger. ~arger juvenile chub~ ~ a more
diversified diet, including terrestrial an aquatic insects. During the
summer, adult bony tail chub fed on terrestrial insects that probably were
taken from the surface. No fish remains were
In the Gila River, Kirsch (188 reported that food of the bony tail chub
consisted "almost entirely of gasteroeods and caddis-worms, which they crush
with their powerful pharyngeals."

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